Book/Report

FZJ-2018-02287

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Absolutmessung der Strahlungsverluste eines Tokamaks im Bereich der ultraweichen Röntgenstrahlung

Petzold, H.-C. (Corresponding author)FZJ*

1983
Kernforschungsanlage Jülich, Verlag Jülich

Please use a persistent id in citations: http://hdl.handle.net/2128/17986

Report No.: Juel-1862

Abstract: In this work experiments were performed to investigate the question to which extent spectroseopic measurements in the ultrasoft x-ray region ($\lambda$= 1 - 10 nm) are a useful technique für diagnosing the relatively cool edge region (T$_{e}$ $\approx$100-200 eV)of fusion-oriented plasmas. Object of these measurements was the plasma centre of a wall tokamak where the plasma parameters are comparable to those in the edge region mentioned above. The measurements were done a Bragg-spectrometer using either TAP (2d = 2.59 nm) of lead stearate (2d = 10.04 nm) as alanyzer crystal. This allowed to cober the whole spectrum between 0.5 and 9 nm with $\underline{one}$ instrument. Using a photoncounting detector the spectrometer/detector system was absolutely calibrated by measuring the transmission of its different components by means of monochromatic x-ray radiation. For the investigated tokamak plasma intense line spectra in the region 1.4 nm $\le \lambda \le$ 2.2 nm as well as at $\lambda \le$ 4.4 nm have been observed, where the former was caused by the high ionization stages of oxygen (0VII and 0VIII), whereas the latter could be explained by Ar- to Na-like ions of the metallic impurities Fe, Cr, and Ni. The plasma' s central electron temperature T$_{e}$ could be determined from the intensity ratio of different oxygen lines using a corona model. Good agreement was found with the results fror measurements of the continuous emission at $\lambda \le$1 nm. With the temperature obtained in this way the relatively easy and exact measurement of the absolute line intensities allowed to determine the ion densities n$_{i,z}$ of oxygen and the metallic impurities. The results are compatible with both those obtained for the same plasma using different methods and with those cited in literature für other tokamaks.The energy balance of the plasma was considered including the measured radiation losses p$^{rad}$. lt was shown that for theplasma investigated here only the emission in the edge region (where T$_{e}$ $\lesssim$ 30 eV) contributed to the energy balance significantly. lt was also shown, however that with the considerably lower power densities of the Ohmic heating in large tokamaks, metallic impurity concentrations of less than 10% of the oxygen concentration are sufficient to extend the radiation-dominated edge region (caused by oxygen) to radii where T$_{e}$ $\approx$ 100 - 200 eV. In contrast to the diagnostic technique applied here, the methods for determining T$_{e}$, n$_{i,z}$ and p$^{rad}$ that are successfully applied to the plasma centre of large tokamaks generally fail in the plasma edga region for lack of intensity. Therefore, spectroscopic measurements in the ultrasoft x-ray region are a valuable addition to these methods wigh regard to a comprehensive diagnosis of fusion plasmas.

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Contributing Institute(s):

1. Publikationen vor 2000 (PRE-2000)

Research Program(s):

1. 899 - ohne Topic (POF3-899) (POF3-899)

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